We have an cloud-based app that sends emails to us and our customers. For example puposes, the address being used to send is firstname.lastname@example.org
From the logs it appears that when sending to external recipients from this app (ie: to hotmail.com, gmail.com, etc), the mail is delivered successfully. When the app trys to send an email to us (ie: email@example.com), it appears that ironmail is rejecting the email with the above message (Unknown address error 556-Cannot accept message from this email address)
I'm assuming it is because the ironmail sees that it is trying to send using a domain that it is configured to protect and the source IP address does not match any of the configured IPs on its list?
Which setting should I look at to address this? IP Whitelisting, IP Relay or some other setting?
Following the online help you should put the IP to the allow relay list:
"Reject Invalid MailFrom
Select this checkbox to enable Email Gateway to reject mail from an address that is part of the routing domain but is not in the Allow Relay list."